We hypothesize that patients on HAART, while having recovered memory T cell responses to recall antigens, have a persistently reduced capacity to mount primary immune pesponses compared to HIV-uninfected controls. We shall test this by evaluating primary immune responses in a cohort of chronically HIV-infected patients on HAART (henceforth referred to as "patients"), and will compare these responses with those of a cohort of healthy, age and sex-matched individuals without HIV infection (henceforth referred to as "controls"). Our approach will be to characterize patients and controls immunologically, and subsequently to immunize all study subjects with keyhole limpet hemocyanin (KLH), and measure the response to the vaccine. Base line immunologic characterization will consist of evaluations of CD4{+} T cell naive/memory phenotype, memory T cell proliferative responses, T cell cytokine secreting capacity, and in vitro IL-12 secretory responses. By correlating these base line measurements with KLH responses, we shall seek to identify base line immunologic parameters which may predict primary immune function in patients on HAART. Study Objectives Primary: 1. To ascertain the range of primary immune responses to vaccination with KLH and polyvalent pneumococcal polysaccharide vaccine in individuals with chronic HIV infection receiving HAART, compared to HIV-uninfected healthy controls. 2. To identify immunologic predictors of primary immune responsiveness in chronically-infected patients on HAART. Secondary: 1. To evaluate the effect of KLH and PPS immunization on HIV turnover in patients receiving HAART.